In air-cooling systems, process-heat removal is carried out by means of convective heat transfer by ambient air via bundles of surface heat exchangers. This requires a very large air-cooling surface even in the case of a medium-sized process or power plant block.
It is a long used technique for reducing the footprint (footing area) of air coolers and dry cooling towers not to dispose the air-cooling bundles adjacently to each other in one plane, i.e. perpendicular to the original air flow direction, but to arrange those at angles significantly less than 180° (e.g. 60°) with respect to each other. So, the front face of the air-cooling bundles (columns) is arranged at an angle less than perpendicular to the original flow direction of the cooling air. Therefore, the front face and the surface of air-coolers on a given footprint or around at a given diameter can be successfully increased within certain limits.
Various arrangements have been developed so far, nevertheless, in case of high- or even medium-capacity air-coolers, almost exclusively the air-cooling arrangement resulting the aforementioned “folded” air flow is applied, irrespective of the fact whether the coolers are horizontally or vertically arranged, or whether it is direct or indirect air-cooling.
As a result of the “folded” arrangement, the air-coolers have multiple V or A-shaped surfaces (i.e. having triangular cross-sections), significantly increasing the front face of the air-coolers arranged in a given footprint, i.e. the cooling capacity of the cooling tower.
A known efficient air-cooling arrangement is applied in the so-called Heller-system. The constructional units of the air coolers, in view of their respective cross section perpendicular to the longitudinal direction, consist of two cooling columns arranged at an angle of α=40° to 60° with respect to each other, as legs of an isosceles triangle, where the third side is open (optionally arranged with shutters) for the incoming cooling air. These so-called cooling deltas have been in use since the 1950s (see e.g. in the literature: Balogh, A., Szabó, Z., Advanced Heller System to Improve Economics of Power Generation, EPRI Conference on Advanced Cooling Strategies/Technologies, June 2005, Sacramento, Calif.) and this known arrangement is shown in FIGS. 1-3. Cooling deltas 11 illustrated in top view in FIGS. 1 and 2 and in three-dimensional view in FIG. 3, are disposed in prior art systems vertically along a path 10 having the form of a circle (or a polygon approximating a circle). The path 10 typically follows the base-outline of a cooling tower. According to the invention, path refers to a trace defined by respective points in identical positions of the essentially identically formed cooling deltas. The entire air-cooling surface is made up of the cooling deltas 11. The cooling air exhibits a single-folded flow path indicated by arrows in top view, following the geometry of the individual cooling deltas. The flow of the cooling air is driven by means of a natural draft tower disposed over the arrangement or by means of fans arranged in a vertical plane on the inner or outer side.
The ever increasing demand for cooling capacity of power station blocks, resulting from the demand for increasing the block size and for reaching even lower condensational temperature or cooling water temperature at a given outside temperature, is an increasing challenge for air cooler system manufacturers. These challenges can be overcome by decreasing the angle of the cooling deltas and by increasing their respective lengths (one basic case of this being provided by stacking the separate air coolers one above the other in a storey-like array, as disclosed e.g. in U.S. Pat. No. 3,434,529 or later in US 2010/276129 A1) only to a certain limit, so as to avoid extra costs and decline in efficiency incurred by deteriorating thermal technology and constructional problems. In the case of state-of-the-art, high capacity nuclear power stations, up to three to four natural draft air-cooling towers are required for a single power plant block so that the dry or dry-wet cooling system be competitive in terms of efficiency with wet cooling, which by the way, has significantly higher water-consumption, i.e. is environmentally less desirable. These numbers of cooling towers may cause, especially in the case of a multi-unit nuclear power station premise, serious problems in terms of placement; moreover, efficiency would also be negatively affected by the interference between the towers, GB 971 480 discloses an air-cooled condenser having cooling elements arranged zig-zag in horizontal cross-section.